Field of the Invention
This invention relates generally to a system and method for detecting flashback events in a combustor of a gas turbine engine and, more particularly, to a fiber optic distributed sensing system employing Rayleigh backscattering and swept-wavelength interferometry for measuring temperature and detecting flashback events at many locations within a combustor of a gas turbine engine.
Discussion of the Related Art
The world's energy needs continue to rise which provides a demand for reliable, affordable, efficient and environmentally-compatible power generation. A gas turbine engine is one known machine that provides efficient power, and often has application for an electric generator in a power plant, or engines in an aircraft or a ship. A typically gas turbine engine includes a compressor section, a combustion section and a turbine section. The compressor section provides a compressed airflow to the combustion section where the air is mixed with a fuel, such as natural gas. The combustion section includes a plurality of circumferentially disposed combustors that receive the fuel to be mixed with the air and ignited to generate a working gas. The working gas expands through the turbine section and is directed across rows of blades therein by associated vanes As the working gas passes through the turbine section, it causes the blades to rotate, which in turn causes a shaft to rotate, thereby producing mechanical work
Each combustor includes a fuel injector, orifices for receiving compressed air and an igniter for igniting the fuel/air mixture to create a flame in a combustion basket The pressure and volume of both the injected fuel and the air are carefully controlled for a particular combustor so that the flame is propelled forward into a transition duct to the turbine section. As the operating conditions of the turbine engine vary and change, a failure mode could occur where the pressure and flow volume of the fuel and/or air causes a flashback condition where the flame travels backwards in a direction away from the turbine section. If the engine operating parameters are not immediately changed to remove the flashback condition, the flame flashback could cause damage to components upstream of the combustion area in the combustion basket because many of those components are not designed for such high temperatures.
It is known in the art to provide various types of sensors, such as high temperature thermocouples or optical detectors, such as fiber Bragg grating (FBG) sensors, strategically positioned behind the combustion area in the combustion basket of a combustor to detect flame flashback by detecting higher than normal temperatures. If flame flashback is detected by one of the detectors, then the system engine controller will take some immediate action, possibly system shutdown, to remove the flashback condition. However, the number of thermocouples and/or optical sensors that can be provided in the combustor is limited because of limits of the ability to configure and position multiple thermocouple sensors in the combustion basket or the spatial resolution of the optical detectors provided in an optical sensor. Because the resolution is limited, the ability to quickly detect a flashback condition and specifically identify the location of the flashback condition is correspondingly limited. For example, the flame may flash back to a location in the combustion basket where a sensor does not exist, thus limiting the ability to detect that flashback condition.